The present invention relates to an oscillation circuit applicable to various kinds of electronic apparatuses as a clock source and, more particularly, to an oscillation circuit of the type using a quartz oscillator and free from the accidental fall of oscillation level and the accidental stop of oscillation.
A conventional oscillation circuit, particularly one using a quartz oscillator, oscillates continuously only when the resistance Rx of the oscillator relative to the frequency and the negative resistance --Ro of the circuit satisfy a relation .vertline.-Ro.vertline.&gt;.vertline.Rx.vertline.. The oscillation is stabilized when the oscillation level increases until .vertline.Rx.vertline.=.vertline.--Ro.vertline. holds.
However, the problem with the conventional circuit is that when the negative resistance --Ro of the circuit decreases due to, for example, a change in ambient temperature, the oscillation level also fails. Further, when the negative resistance --Ro of the circuit decreases to below the resistance Rx of the oscillator, the circuit practically stops oscillating.